Different documents describing different procedures for obtaining nanofibrillated cellulose are known in the state of the art.
In U.S. Pat. No. 4,483,743, nanofibrillated cellulose is obtained from a liquid suspension of virgin cellulose that is subjected to a warming-up pre-treatment of 50° C. to 80° C., being processed by passing it through a high pressure homogeniser.
WIPO publication WO2011/051882 A1 describes a procedure for obtaining nanofibrillated cellulose obtained from cotton, cereals, hard and soft woods that are subjected to a pre-treatment with enzymes, being processed by a twin-screw extruder.
In WIPO publication WO2010/149711 A2, the raw material from which nanofibrillated cellulose is obtained is recycled white paper, colour paper of different colours or bleached papers, which are subjected to a previous treatment comprising the use of a paper shredder with an interchangeable hammer mill suitable for the preparation of hemp, cereal straw and other lignocellulosic materials, related to the separation of foreign (opposite) material (wood, metal, stone, plastics, etc.) and a cleaning system, including the elimination of powder.
Finally, WIPO publication WO2011/055148 describes an apparatus and a method for processing cellulose fibres, which leaves the source of cellulosic material very open, not using just paper, using some pre-treatments similar to those from the above patent.
However, none of the above patents describes a procedure for obtaining nanofibrillated cellulose starting from recovered paper, obtaining nanofibrillated cellulose having similar features to that obtained from virgin cellulose.